Method of making a light emitting device having a molded encapsulant

ABSTRACT

Disclosed herein is a method of making a light emitting device having an LED die and a molded encapsulant made by polymerizing at least two polymerizable compositions. The method includes: (a) providing an LED package having an LED die disposed in a reflecting cup, the reflecting cup filled with a first polymerizable composition such that the LED die is encapsulated; (b) providing a mold having a cavity filled with a second polymerizable composition; (c) contacting the first and second polymerizable compositions; (d) polymerizing the first and second polymerizable compositions to form first and second polymerized compositions, respectively, wherein the first and second polymerized compositions are bonded together; and (e) optionally separating the mold from the second polymerized composition. Light emitting devices prepared according to the method are also described.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional PatentApplication No. 60/822,714, filed Aug. 17, 2006, the disclosure of whichis incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The invention relates to a method of making a light emitting devicehaving an light emitting diode (LED) die and a molded encapsulant,wherein the molded encapsulant is made by polymerizing at least twopolymerizable compositions.

BACKGROUND

Encapsulation of semiconductor devices has traditionally beenaccomplished using a transfer molding process in which a thermosetmolding compound (typically a solid epoxy preform) is dielectricallypreheated and then placed into a pot of a molding tool. A transfercylinder, or plunger, is used to push the molding compound into a runnersystem and gates of the mold. The molding compound then flows over thechips, wirebonds, and leadframes, encapsulating the semiconductordevice. Most transfer molding processes suffer from significant problemsarising from high operating temperatures (the molding compound is asolid at room temperature) and high pressures required to fill the mold(even in the melt state, the molding compound has a high viscosity, andthe viscosity increases further with reaction). These problems can leadto incomplete mold filling, thermal stresses (since the reactiontemperature is much higher than the final use temperature), and wiresweep. In general, there is a need for new methods of making LED deviceshaving molded encapsulants.

SUMMARY

Disclosed herein is a method of making a light emitting device having anLED die and a molded encapsulant, wherein the molded encapsulant is madeby polymerizing at least two polymerizable compositions.

In one aspect, the method for making the light emitting devicecomprises: (a) providing an LED package comprising an LED die disposedin a reflecting cup, the reflecting cup filled with a firstpolymerizable composition such that the LED die is encapsulated; (b)providing a mold having a cavity filled with a second polymerizablecomposition; (c) contacting the first and second polymerizablecompositions; (d) polymerizing the first and second polymerizablecompositions to form first and second polymerized compositions,respectively, wherein the first and second polymerized compositions arebonded together; and (e) optionally separating the mold from the secondpolymerized composition.

In another aspect, the method for making the light emitting devicecomprises: (a) providing an LED package comprising an LED die disposedin a reflecting cup, the reflecting cup filled with a firstpolymerizable composition such that the LED die is encapsulated; (b)providing a transparent mold having a cavity filled with a secondpolymerizable composition; (c) polymerizing the first polymerizablecomposition to form a first partially polymerized composition, whereinpolymerizing the first polymerizable composition comprises applyingactinic radiation having a wavelength of 700 nm or less; (d) invertingthe LED package to contact the first partially polymerized compositionand the second polymerizable composition; and (e) polymerizing thesecond polymerizable composition to form a second partially polymerizedcomposition, wherein polymerizing the second polymerizable compositioncomprises applying actinic radiation having a wavelength of 700 nm orless.

In another aspect, the method for making the light emitting devicecomprises: (a) providing an LED package comprising an LED die disposedin a reflecting cup, the reflecting cup filled with a firstpolymerizable composition such that the LED die is encapsulated; (b)providing a transparent mold having a cavity filled with a secondpolymerizable composition; (c) polymerizing the second polymerizablecomposition to form a second partially polymerized composition, whereinpolymerizing the second polymerizable composition comprises applyingactinic radiation having a wavelength of 700 nm or less; (d) invertingthe mold to contact the first polymerizable composition and the secondpartially polymerized composition; and (e) polymerizing the firstpolymerizable composition to form a first partially polymerizedcomposition, wherein polymerizing the first polymerizable compositioncomprises applying actinic radiation having a wavelength of 700 nm orless.

In another aspect, the method for making the light emitting devicecomprises: (a) providing an LED package comprising an LED die disposedin a reflecting cup, the reflecting cup filled with a firstpolymerizable composition such that the LED die is encapsulated; (b)providing a mold having a cavity filled with a second polymerizablecomposition; (c) polymerizing the first and second polymerizablecompositions to form first and second partially polymerizedcompositions, respectively, wherein polymerizing comprises applyingactinic radiation having a wavelength of 700 nm or less; and (d)contacting the first and second partially polymerized compositions.

In another aspect, the method for making the light emitting devicecomprises: (a) providing an LED package comprising an LED die disposedin a reflecting cup, the reflecting cup filled with a firstpolymerizable composition such that the LED die is encapsulated; (b)providing a mold having a cavity filled with a second polymerizablecomposition; (c) polymerizing the first polymerizable composition toform a first partially polymerized composition, wherein polymerizing thefirst polymerizable composition comprises heating; (d) inverting the LEDpackage to contact the first partially polymerized composition and thesecond polymerizable composition; and (e) polymerizing the secondpolymerizable composition to form a second partially polymerizedcomposition, wherein polymerizing the second polymerizable compositioncomprises heating.

In another aspect, the method for making the light emitting devicecomprises: (a) providing an LED package comprising an LED die disposedin a reflecting cup, the reflecting cup filled with a firstpolymerizable composition such that the LED die is encapsulated; (b)providing a mold having a cavity filled with a second polymerizablecomposition; (c) polymerizing the second polymerizable composition toform a second partially polymerized composition, wherein polymerizingthe second polymerizable composition comprises heating; (d) invertingthe mold to contact the first polymerizable composition and the secondpartially polymerized composition; and (e) polymerizing the firstpolymerizable composition to form a first partially polymerizedcomposition, wherein polymerizing the first polymerizable compositioncomprises heating.

In another aspect, the method for making the light emitting devicecomprises: (a) providing an LED package comprising an LED die disposedin a reflecting cup, the reflecting cup filled with a firstpolymerizable composition such that the LED die is encapsulated; (b)providing a mold having a cavity filled with a second polymerizablecomposition; (c) polymerizing the first and second polymerizablecompositions to form first and second partially polymerizedcompositions, respectively, wherein polymerizing comprises heating; and(d) contacting the first and second partially polymerized compositions.

In another aspect, the method for making the light emitting devicecomprises: (a) providing an LED package comprising an LED die disposedin a reflecting cup, the reflecting cup filled with a firstpolymerizable composition such that the LED die is encapsulated, whereinthe first polymerizable composition is thixotropic; (b) providing a moldhaving a cavity filled with a second polymerizable composition, whereinthe second polymerizable composition is thixotropic; (c) contacting thefirst and second polymerizable compositions; and (d) polymerizing thefirst and second polymerizable compositions to form first and secondpolymerized compositions, respectively, wherein the first and secondpolymerized compositions are bonded together, and polymerizing comprisesapplying actinic radiation having a wavelength of 700 nm or less and/orheating.

Also disclosed herein is an LED device prepared according to any one ofthe methods disclosed herein.

These and other aspects of the invention will be apparent from thedetailed description and drawings below. In no event should the abovesummary be construed as a limitation on the claimed subject matter,which subject matter is defined solely by the claims as set forth hereinand as may be amended during prosecution.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1 and 2 are schematic diagrams of known LED devices.

FIG. 3 shows a top down perspective of an array of LEDs on a lead frame.

FIG. 4 shows a top down perspective of a mold.

FIGS. 5 a-5 i are schematic diagrams of methods used to make LED devicesaccording to embodiments of the present disclosure.

FIG. 6 is a schematic diagram of an LED device according to anembodiment of the present disclosure.

The invention may be more completely understood in consideration of thefollowing detailed description in connection with the Figures describedabove. The Figures are illustrative examples only.

DETAILED DESCRIPTION

This application is related to the following which are incorporatedherein by reference: U.S. Pat. No. 7,192,795 B2 (Boardman et al.); andU.S. Ser. Nos. 11/252,336 (Boardman et al.); 11/255,711 (Boardman etal.); 11/255,712 (Boardman et al.); 11/551,309 (Thompson et al.);11/551,323 (Thompson et al.); and 11/741,808 (Thompson et al.).

LED devices can be manufactured in a variety of configurations, many ofwhich incorporate one or two conductive metal wires connecting thesemiconductor die to electrodes in the base of the LED package. FIG. 1is a schematic diagram of known LED device 100 with one wire bond 130bonded to LED die 110. The LED die is connected to electrodes 120 a and120 b, which are disposed on substrate 140 inside reflecting cup 160.The LED die is encapsulated with encapsulant 150 which serves to bothincrease the amount of light extracted from the die as well as toprotect components from physical damage.

FIG. 2 is a schematic diagram of known LED device 200 with one wire bond220 bonded to LED die 210. The LED die is mounted on substrate 250 andis encapsulated by dome-shaped encapsulant 230 and outer shell 240. Theouter shell is a separately molded lens used to mold the encapsulant.The convex shape of the encapsulant and outer shell, optically coupledto the LED die, can be used to control the distribution of light emittedby the die and can also improve efficiency and light output. Performanceof an LED device is improved because the amount of light being recycledis minimized. This is beneficial because light from the LED die canimpinge on the lens/air interface at an angle closer to the surfacenormal for the majority of angles of light emitted from the LED die.This helps to minimize Fresnel reflection at the lens/air interface andresults in a more efficient LED device with increased total radiant fluxor light output.

LED devices having a separately molded lens, such as LED device 200, areexpensive and complex to manufacture. For one, the lens must be madeseparately, for example, by injection molding, and in additional steps,the lens must be attached to the package in a pick and place operationand the cavity formed by the lens and the package must then be filledwith encapsulant resin. Most injection moldable plastics that aresuitable for making hard lenses have refractive indices significantlyhigher than the most photostable silicone materials used forencapsulating an LED die. This can lead to non-optimal LED performance.

The method disclosed herein provides several advantages. The method canbe used to manufacture an LED device using at least two polymerizablecompositions, one to encapsulate an LED die, and one to provide a lenswith an output surface that is optically coupled to the die such thatlifetime, efficiency, and light output of the device are improved. Withan appropriate combination of polymerizable compositions and cureconditions, both encapsulation and formation of the lens with an outputsurface can be carried out in relatively few steps such that formationof the LED device is fast and economical.

Another advantage is that the polymerizable compositions may bedifferent from each other as described in Ser. No. 11/741,808 (Thompsonet al.). For example, a polymerizable composition that forms a softencapsulant, and which provides lower stress in the LED package, can beused around the LED die and wire bond(s), and a different polymerizablecomposition that forms a hard molded element can be used to provide theoutput surface. For another example, the refractive index of the moldedelement can be selected to be less than that of the encapsulant.

Another advantage is that actinic radiation can be used such thatharmful temperatures can be avoided. Yet another advantage is that themethod is amenable to large scale manufacturing processes such that aplurality of LED devices can be manufactured simultaneously or nearlysimultaneously.

The method disclosed herein comprises providing an LED packagecomprising an LED die disposed on a substrate in a reflecting cup.

The reflecting cup is filled with a first polymerizable composition suchthat the LED die is encapsulated. Suitable materials for the firstpolymerizable composition include those that are thermally stable,photochemically stable, clear and colorless in nature. Herein, thermallystable refers to a material that does not chemically degrade uponprolonged exposure to heat, particularly with respect to the formationof colored or light absorbing degradation products. Herein,photochemically stable refers to a material that does not chemicallydegrade upon prolonged exposure to actinic radiation, particularly withrespect to the formation of colored or light absorbing degradationproducts.

The first polymerizable composition may comprise a silicone gel,silicone gum, silicone fluid, organosiloxane, polysiloxane, colorlesspolyimide, polyphosphazene, sol-gel, epoxy, (meth)acrylate,epoxy-functional silicone, or (meth)acrylated silicone. For example, thefirst polymerizable composition may comprise a silicon-containing resincomprising silicon-bonded hydrogen and aliphatic unsaturation. Foranother example, the first polymerizable composition may comprise anorganosiloxane liquid or gel material. Preferred liquid or gel materialsare curing silicone fluids that build viscosity on irradiation, siliconegums made from low molecular weight fluids that cure and chain extendinto gum like materials (i.e. no crosslinking) on irradiation with UVlight, curing silicone gels, and curing silicone fluids that polymerizeto form elastomeric or nonelastomeric materials.

In one embodiment, the first polymerizable composition can bephotopolymerizable, i.e., can be polymerized by applying actinicradiation having a wavelength of 700 nm or less, preferably from 250 to500 nm. If desired, in order to accelerate polymerization, the firstpolymerizable composition can be polymerized by simultaneously applyingactinic radiation having a wavelength of 700 nm or less and heating at atemperature of less than 150° C., less than 120° C., less than 60° C.,or at 25° C. or less. Examples of sources of actinic radiation includetungsten halogen lamps, xenon arc lamps, mercury arc lamps, incandescentlamps, germicidal lamps, fluorescent lamps, LEDs, or lasers.

In one embodiment, the first polymerizable composition comprises aphotopolymerizable composition of a silicon-containing resin havinggroups incorporating aliphatic unsaturation and silicon-bonded hydrogen.The groups undergo a hydrosilylation reaction which is initiated in thepresence of a metal-containing catalyst and actinic radiation having awavelength of 700 nm or less. Such compositions are described in U.S.Pat. No. 7,192,795 B2 (Boardman et al.) and references cited therein.They can be useful when rapid cure times of seconds to less than 30minutes are desirable. The silicon-containing resin can includemonomers, oligomers, polymers, or mixtures thereof. The silicon-bondedhydrogen and the aliphatic unsaturation may or may not be present in thesame molecule. Furthermore, the aliphatic unsaturation may or may not bedirectly bonded to silicon.

The silicon-containing resin can comprise an organosiloxane (i.e., asilicone) which includes an organopolysiloxane. The silicon-containingresin can include a silicone component having at least two sites ofaliphatic unsaturation (e.g., alkenyl or alkynyl groups) bonded tosilicon atoms in a molecule and an organohydrogensilane and/ororganohydrogenpolysiloxane component having at least two hydrogen atomsbonded to silicon atoms in a molecule. Preferably, a silicon-containingresin includes both components, with the silicone containing aliphaticunsaturation as the base polymer (i.e., the major organosiloxanecomponent in the composition.) Preferred silicon-containing resins areorganopolysiloxanes. Such resins typically comprise at least twocomponents, at least one of which contains aliphatic unsaturation and atleast one of which contains silicon-bonded hydrogen. Curable onecomponent organopolysiloxane resins are possible if the single resincomponent contains both aliphatic unsaturation and silicon-bondedhydrogen.

Organopolysiloxanes that contain aliphatic unsaturation are preferablylinear, cyclic, or branched organopolysiloxanes comprising units of theformula R¹ _(a)R² _(b)SiO_((4-a-b)/2) wherein: R¹ is a monovalent,straight-chained, branched or cyclic, unsubstituted or substitutedhydrocarbon group that is free of aliphatic unsaturation and has from 1to 18 carbon atoms; R² is a monovalent hydrocarbon group havingaliphatic unsaturation and from 2 to 10 carbon atoms; a is 0, 1, 2, or3; b is 0, 1, 2, or 3; and the sum a+b is 0, 1, 2, or 3; with theproviso that there is on average at least 1 R² present per molecule.Organopolysiloxanes that contain aliphatic unsaturation preferably havean average viscosity of at least 5 mPa·s at 25° C.

Organopolysiloxanes that contain silicon-bonded hydrogen are preferablylinear, cyclic or branched organopolysiloxanes comprising units of theformula R¹ _(a)H_(c)SiO_((4-a-c)/2) wherein: R¹ is as defined above; ais 0, 1, 2, or 3; c is 0, 1, or 2; and the sum of a+c is 0, 1, 2, or 3;with the proviso that there is on average at least 1 silicon-bondedhydrogen atom present per molecule. In one embodiment, at least 90 molepercent of the R¹ groups are methyl. In another embodiment, the R¹groups are methyl, phenyl, or a combination thereof. Organopolysiloxanesthat contain silicon-bonded hydrogen preferably have an averageviscosity of at least 5 mPa·s at 25° C.

Organopolysiloxanes that contain both aliphatic unsaturation andsilicon-bonded hydrogen preferably comprise units of both formulae R¹_(a)R² _(b)SiO_((4-a-b)/2) and R¹ _(a)H_(c)SiO_((4-a-c)/2). In theseformulae, R¹, R², a, b, and c are as defined above, with the provisothat there is an average of at least 1 group containing aliphaticunsaturation and 1 silicon-bonded hydrogen atom per molecule.

The molar ratio of silicon-bonded hydrogen atoms to aliphaticunsaturation in the silicon-containing resin (particularly theorganopolysiloxane resin) may range from 0.5 to 10.0 mol/mol, preferablyfrom 0.8 to 4.0 mol/mol, and more preferably from 1.0 to 3.0 mol/mol.

Organopolysiloxane resins having a significant fraction of the R¹ groupsas phenyl or other aryl, aralkyl, or alkaryl are preferred, because theincorporation of these groups provides materials having higherrefractive indices than materials wherein all of the R¹ radicals are,for example, methyl. As described herein, particles may be used in thefirst polymerizable composition in order to increase refractive index.

The compositions described in U.S. Pat. No. 7,192,795 B2 (Boardman etal.) also include a metal-containing catalyst that enables cure of thematerial via radiation-activated hydrosilylation. These catalyststypically include complexes of precious metals such as platinum,rhodium, iridium, cobalt, nickel, and palladium. The preciousmetal-containing catalyst preferably contains platinum. Certainpreferred platinum-containing catalysts are selected from the groupconsisting of Pt(II) β-diketonate complexes,(η⁵-cyclopentadienyl)tri(σ-aliphatic)platinum complexes, andC₇₋₂₀-aromatic substituted (η⁵-cyclopentadienyl)tri(σ-aliphatic)platinumcomplexes. Such catalysts are used in an amount effective to acceleratethe hydrosilylation reaction and preferably in an amount of no greaterthan 1000 parts of metal per one million parts of the composition.

In another embodiment, the first polymerizable composition comprises anonphotopolymerizable composition of a silicon-containing resin havinggroups incorporating aliphatic unsaturation and silicon-bonded hydrogen.For example, polymerization of the silicon-containing resin may becarried out by applying heat to the nonphotopolymerizable compositioncomprising the silicon-containing resin and a suitable catalyst.Catalysts include complexes of precious metals such as platinum,rhodium, iridium, cobalt, nickel, and palladium and, for example, inU.S. Pat. Nos. 2,823,218 (Speier et al), 3,419,593 (Willing), 3,715,334and 3,814,730 (Karstedt), 4,421,903 (Ashby), 3,220,972 (Lamoreaux),4,613,215 (Chandra et al), and 4,705,765 (Lewis). In one embodiment, thenonphotopolymerizable composition comprises a metal-containing catalystcomprising a platinum vinylsiloxane complex.

As described above, the amounts of the metal-containing catalysts usedin the photopolymerizable composition may depend on a variety of factorssuch as whether actinic radiation and/or heat is being used, theradiation source, amount of time, temperature, etc., as well as on theparticular chemistry of the silicon-containing resin, its reactivity,the amount present in the light emitting device, etc. In someembodiments, the first and second metal-containing catalysts may beindependently used in an amount of at least 1 part, and more preferablyat least 5 parts, per one million parts of the photopolymerizablecomposition. Such catalysts are preferably included in amounts of nogreater than 1000 parts of metal, and more preferably no greater than200 parts of metal, per one million parts of the photopolymerizablecomposition.

In one embodiment, the first polymerizable composition comprises a firstpartially polymerized composition. Partial polymerization may be used toincrease the viscosity and/or gel the composition such that it does notflow out of the reflecting cup when the LED package is tilted or turnedover. For example, the LED package may be inverted as described below.Ideally, the surface of the first partially polymerized composition hasat least some tackiness or is sticky so that the adhesion between thefirst and second polymerized compositions is enhanced either by chemicalbonding or by physical bonding, for example, by chain entanglementsbetween the first and second polymerized compositions and/or non-bondedinteractions.

In one embodiment, a nonpolymerizable composition may be used instead ofthe first polymerizable composition. That is, the method may comprise:(a) providing an LED package comprising an LED die disposed in areflecting cup, the reflecting cup filled with a nonpolymerizablecomposition such that the LED die is encapsulated; (b) providing a moldhaving a cavity filled with a second polymerizable composition; (c)contacting the nonpolymerizable composition and the second polymerizablecomposition; (d) polymerizing the second polymerizable composition toform a second polymerized composition, wherein the nonpolymerizable andsecond polymerized compositions are bonded together; and (e) optionallyseparating the mold from the second polymerized composition.

The nonpolymerizable composition may comprise anorganosiloxane-containing liquid, gel, elastomeric solid, ornonelastomeric solid. The nonpolymerizable composition may also comprisepolyimide, polyphosphazene, epoxy, (meth)acrylate, and sol-gel material.For example, the nonpolymerizable composition may comprise a siliconegel, silicone gum, silicone fluid, organosiloxane, polysiloxane,colorless polyimide, polyphosphazene, sol-gel, epoxy-functionalsilicone, or (meth)acrylated silicone.

The method disclosed herein comprises providing a mold having a cavity.The cavity is shaped to impart a desired complimentary shape to theouter surface of the second polymerizable composition. Any materialcapable of being formed into a mold may be used, and in general, it isusually desirable for the mold material to have a glass transitiontemperature greater than the particular temperature(s) used in a methodof making the light emitting device as described below. Useful moldmaterials are described in U.S. Ser. Nos. 11/551,309 (Thompson et al.)and 11/551,323 (Thompson et al.) and include polymeric materials such asfluoroelastomers, polyolefins, polystyrene, polyesters, polyurethanes,polyethers, polycarbonates, polymethyl methacrylate; inorganic materialscomprising ceramics, quartz, sapphire, metals, and certain glasses; andorganic-inorganic hybrid materials.

The mold may be transparent, particularly when the method comprisesphotopolymerization after any of the first and second compositions arecontacted with each other. The first and second compositions may also bepartially polymerized compositions or some combination thereof. It isgenerally desirable for the mold to be transparent at the wavelength ofthe actinic radiation. In this regard, transparent refers totransmission greater than 50%, greater than 60%, or greater than 70% atthe wavelength of the actinic radiation. Examples of transparent moldmaterials include transparent plastics and ceramics as described above.The mold can also be non-transparent such as an opaque ceramic, anopaque plastic, or a metal. The mold can be fabricated by conventionalmachining, diamond turning, contact lithography, projection lithography,interference lithography, etching, or any other suitable technique. Themold may be an original master mold or a daughter mold thereof. Moldingmay be referred to as reactive embossing. As described below, the moldmay comprise more than one cavity. For example, the mold may comprise athin sheet of plastic material with formed cavities, such as can beproduced in a vacuum molding process or can be thicker blocks ofmaterial with formed or machined cavities. The surface of the mold thatcontacts the second polymerizable composition may be coated with arelease material in order to facilitate removal of the mold from thecomposition. Examples of release materials include household detergentsin water and fluorocarbon release agents.

The mold may be shaped so as to impart any useful structure on thesurface of the second polymerizable composition. Suitable structuredsurfaces are described in U.S. Ser. Nos. 11/551,309 (Thompson et al.)and 11/551,323 (Thompson et al.). For example, the mold may be shaped soas to form a refractive lens on the LED. Lensing refers to the uniform(or nearly uniform) curvature of a substantial portion of the surface ofthe encapsulant to form a positive or negative lens, the diameter ofwhich is approximately the size of the package or reflector cup. Ingeneral, a lensed surface can be characterized by a “radius ofcurvature.” The radius of curvature can be either positive, denoting aconvex surface or negative denoting a concave surface or infinitedenoting a flat surface. Lensing can improve light extraction byreducing the total internal reflections of light incident at theencapsulant-air interface. It can also change the angular distributionof light emitted from the light emitting device. In one embodiment, themold is shaped to impart a hemispherical lens on the secondpolymerizable composition.

The surface may also be shaped with macrostructures having acharacteristic dimension that is smaller than the package size, but muchlarger than the wavelength of visible light. That is, eachmacrostructure may have a dimension of from 10 μm to 1 mm. The spacingor period between each macrostructure may also be from 10 μm to 1 mm (orabout ⅓ the size of the LED package). Examples of macrostructuresinclude surfaces that, when viewed in cross-section, appear to be shapedlike a sine wave, triangular wave, square wave, rectified sine wave, sawtooth wave, cycloid (more generally curtate cycloid), or rippled. Theperiodicity of the macrostructures may be one- or two-dimensional.Surfaces with one-dimensional periodicity have repeat structures alongonly one major direction of the surface. In one particular example, themold may comprise any of the Vikuiti™ Brightness Enhancement Filmsavailable from 3M Company.

The mold may be shaped to impart a lens structure capable of making amolded encapsulant that can generate a side-emission pattern. Forexample, the molded encapsulant has a central axis, and light enteringthe molded encapsulant is reflected and refracted and eventually exitsin a direction substantially perpendicular to the central axis; examplesof these types of side emitting lens shapes and devices are described inU.S. Pat. No. 6,679,621 B2 and U.S. Pat. No. 6,598,998 B2. For anotherexample, the molded encapsulant has a generally planar surface, with asmoothly curved surface defining a vortex shape that extends into theencapsulant and has the shape of an equiangular spiral that forms into acusp; an example of such a profile is described in U.S. Pat. No.6,473,554 B1, particularly FIGS. 15, 16 and 16A.

Surfaces with two-dimensional periodicity have repeat structures alongany two orthogonal directions in the plane of the macrostructures.Examples of macrostructures with two-dimensional periodicity includerandom surfaces, two-dimensional sinusoids, arrays of cones, arrays ofprisms such as cube-corners, and lenslet arrays. The surface may also beshaped as a Fresnel lens having generally circular symmetry and that canbe designed to replicate the optical properties of any positive ornegative lens while occupying much less volume than a solid lens.

In general, the macrostructures do not need to be uniform in size acrossthe surface. For example, they may get larger or smaller toward theedges of the package, or they may change shape. The surface may consistof any linear combination of shapes described herein.

The surface may also be shaped with microstructures having acharacteristic dimension on a scale similar to the wavelengths ofvisible light. That is, each microstructure may have a dimension of from100 nm to less than 10 μm. Light tends to diffract when it interactswith microstructured surfaces. Thus, the design of microstructuredsurfaces requires careful attention to the wave-like nature of light.Examples of microstructures are one- and two-dimensional diffractiongratings; one-, two-, or three-dimensional photonic crystals; binaryoptical elements; “motheye” anti-reflection coatings; and one- andtwo-dimensional arrays of prisms. The microstructures do not need to beuniform in size across the surface. For example, the elements may getlarger or smaller toward the edges of the package, or they may changeshape. The surface may consist of any linear combination of shapesdescribed herein.

The surface of the encapsulant may comprise structures from all threesize scales. All package surfaces will be lensed with some radius ofcurvature, which could be positive, negative, or infinite. Amacrostructure or microstructure could be added to the lensed surface tofurther enhance light output or to optimize the angular distribution fora given application. A surface could even incorporate a microstructureon a macrostructure on a lensed surface.

The mold is filled with a second polymerizable composition. Suitablematerials for the second polymerizable composition include those thatare thermally stable, photochemically stable, clear and colorless innature, as described above for the first polymerizable composition. Forexample, the second polymerizable composition may comprise anorganosiloxane. For another example, the second polymerizablecomposition is selected from the group consisting of silicon-containingresins comprising silicon-bonded hydrogen and aliphatic unsaturation,epoxy silicones, and (meth)acrylated silicones. Silicon-containingresins comprising silicon-bonded hydrogen and aliphatic unsaturationthat may be used as the second polymerizable composition comprise anorganosiloxane-containing elastomer or a non-elastic solid.

In one embodiment, the second polymerizable composition can bephotopolymerizable, i.e., can be polymerized by applying actinicradiation having a wavelength of 700 nm or less, preferably from 250 to500 nm. If desired, in order to accelerate polymerization, the secondpolymerizable composition can be polymerized by simultaneously applyingactinic radiation having a wavelength of 700 nm or less and heating at atemperature of less than 150° C., less than 120° C., less than 60° C.,or at 25° C. or less. In one embodiment, the second polymerizablecomposition comprises a photopolymerizable composition as describedpreviously, i.e., preferably, the second polymerizable compositioncomprises a silicon-containing resin having groups incorporatingaliphatic unsaturation and silicon-bonded hydrogen, and ametal-containing catalyst that enables cure of the material viaradiation-activated hydrosilylation.

The first and second polymerizable compositions may be the same.Alternatively, the first and second polymerizable compositions may bedifferent from each other. For example, the first and secondpolymerizable compositions may be selected such that the firstpolymerized composition is softer than the second. By softer it is meantthat the first polymerized composition is more easily deformed by anexternal mechanical force than the second polymerized composition. Forexample, the first polymerized composition may have a lower Young'smodulus or lower Shore Hardness.

For the first and second photopolymerizable compositions describedabove, a softer first polymerized composition may be obtained by havinga lower crosslink density than the second. This may be achieved bydecreasing the number of silicon-bonded hydrogen atoms along thebackbone of the silicon-containing resin, and/or by increasing themolecular weight of the segments between crosslinks. Themetal-containing catalyst used in each of the photopolymerizablecompositions can also be varied so that a softer first polymerizedcomposition may be obtained. For example, if the same metal-containingcatalyst is used, then a softer first polymerized composition may beobtained by including less of the catalyst in the firstphotopolymerizable composition. If the same silicon-containing resin isused, then a softer first polymerized composition may be obtained byincluding a less reactive catalyst in the first photopolymerizablecomposition.

The first and second polymerized compositions may also be selected toobtain desired refractive indices. For example, the first and secondpolymerized compositions can have substantially the same refractiveindex. For another example, the first polymerized composition may have arefractive index greater than that of the second. This step down inrefractive index from light emitting chip to the first polymerizedcomposition to the second polymerized composition and finally to air,results in more efficient light extraction from the package due tominimization of light loss due Fresnel reflection and absorption. If thepolymerized compositions have different refractive indices, it ispossible for there to be a thin graded index layer at the interfaceresulting from interdiffusion of the high and low index materials. Thelevel of interdiffusion will be a function of the chemical nature of thematerials, the curing mechanism, and rate of cure.

The first and second polymerizable compositions can comprise one or moreadditives selected from the group consisting of nonabsorbing metal oxideparticles, semiconductor particles, phosphors, sensitizers,antioxidants, pigments, photoinitiators, catalyst inhibitors, andcombinations thereof. If used, such additives are used in amounts toproduced the desired effect.

As described above, it may be desirable for the first encapsulant tohave a refractive index greater than that of the second. This may beachieved by including high refractive index nanometer sized particlesthat may or may not be surface modified. If desired, the nanoparticlescan be selected so that they do not introduce color or scattering to theencapsulant.

Nonabsorbing metal oxide and semiconductor particles that aresubstantially transparent over the emission bandwidth of the LED can beused. For example, a 1 mm thick disk of the nonabsorbing metal oxideand/or semiconductor particles mixed with encapsulant may absorb lessthan about 30% of the light incident on the disk. In other cases themixture may absorb less than 10% of the light incident on the disk.Examples of nonabsorbing metal oxide and semiconductor particlesinclude, but are not limited to, Al₂O₃, ZrO₂, TiO₂, V₂O₅, ZnO, SnO₂,ZnS, SiO₂, and mixtures thereof, as well as other sufficientlytransparent non-oxide ceramic materials such as semiconductor materialsincluding such materials as ZnS, CdS, and GaN. The particles can besurface treated to improve dispersibility in the encapsulant. Examplesof such surface treatment chemistries include silanes, siloxanes,carboxylic acids, phosphonic acids, zirconates, titanates, and the like.Techniques for applying such surface treatment chemistries are known.Silica (SiO₂) has a relatively low refractive index but it may be usefulin some applications, for example, as a thin surface treatment forparticles made of higher refractive index materials, to allow for morefacile surface treatment with organosilanes. In this regard, theparticles can include species that have a core of one material on whichis deposited a material of another type.

If used, the nonabsorbing metal oxide and semiconductor particles arepreferably included in the composition in an amount of no greater than85 wt-%, based on the total weight of the encapsulating material.Preferably, the nonabsorbing metal oxide and semiconductor particles areincluded in the composition in an amount of at least 10 wt-%, and morepreferably in an amount of at least 45 wt-%, based on the total weightof the composition. Generally the particles can range in size from 1nanometer to 1 micron, preferably from 10 nanometers to 300 nanometers,more preferably, from 10 nanometers to 100 nanometers. This particlesize is an average particle size, wherein the particle size is thelongest dimension of the particles, which is a diameter for sphericalparticles. It will be appreciated by those skilled in the art that thevolume percent of metal oxide and/or semiconductor particles cannotexceed 74 percent by volume given a monomodal distribution of sphericalparticles.

In one embodiment, the second polymerized composition is harder than thefirst, and the first polymerized composition has a refractive indexgreater than that of the second.

In one embodiment, the second polymerizable composition comprises asecond partially polymerized composition. Partial polymerization may beused to increase the viscosity and/or gel the composition such that itdoes not flow out of the mold when it is tilted or turned over. Forexample, the mold may be inverted as described below. Ideally, thesurface of the second partially polymerized composition has at leastsome tackiness or is sticky so that the adhesion between the first andsecond polymerized compositions is enhanced either by chemical bondingor by physical bonding, for example, by chain entanglements between thefirst and second polymerized compositions and/or non-bondedinteractions.

In one embodiment, the first and second polymerizable compositionscomprise first and second partially polymerized compositions,respectively, for example, in cases where the mold has a hinge and bothpackage and mold must be tilted.

In one embodiment, the method comprises separating the mold from thesecond polymerized composition to form a molded second polymerizedcomposition. In this case, the method may further comprise heating theLED device to obtain the desired properties of the first and secondcompositions. Heating may be carried out at less than 150° C.

The first and second polymerizable compositions are contacted and thenpolymerized to form first and second polymerized compositions that arebonded together such that they cannot easily be separated, i.e., arehandleable in typical manufacturing processes and in use.

For the purposes of LED device manufacture, LED packages are typicallyprovided as an array of LED packages on lead frame. FIG. 3 shows anillustrative picture of such an array of LED packages on a lead frame300. The LED packages 310 are typically injection molded plastic onto apunched metal lead frame 320. The small circular holes 330 running thelength of the lead frame are holes for guide pins which hold the leadframe under tension on the manufacturing line and provide knownregistration for the array of LED packages. Other arrangements andconstructions of LED packages in an array format exist as well, forexample where the body of the package is made of ceramic material andthe LED packages are provided as a large sheet of ceramic packages. Forthe purpose of the description of the disclosed processes, the arraytype shown in FIG. 3 will be used.

In order to provide a process for molding lenses on an array of packagessimultaneously, it is necessary to provide a mold 400 as shown in FIG.4, which has cavities 410 shaped to produce a desired lens shape. It isimportant that the cavities of the mold be aligned with the LED packageson the lead frame. Placement of optional guide holes 420 in the moldsurface can be used to aid in the registration of the mold cavities withthe LED packages. The mold can be made from a variety of materials andmay or may not be transparent to actinic radiation, particularly UVradiation, which may be used for initiating reaction in thepolymerizable composition. The choice of mold material and designdetermines which of the following embodiments are possible.

For the embodiments shown in FIG. 5 and which are described below, thefirst polymerizable composition may be referred to as encapsulant resinand the second polymerizable composition may be referred to as lensresin or resin. The molded and polymerized lens resin will have anoutput surface.

One embodiment of the molding process is shown in FIG. 5 a in a crosssectional perspective and illustrates the process flow for the casewhere the mold material is transparent to UV radiation. Suitable moldmaterials will have glass transition temperatures greater than thetemperatures used for the process. Such mold materials are described inU.S. Ser. Nos. 11/551,309 (Thompson et al.) and 11/551,323 (Thompson etal.) and include, but are not limited, to fluorinated molds such asthose fabricated from Teflon or glass molds that have been treated withrelease agents. Plastic molds can be made of thin sheet like materialswith formed cavities, such as can be produced in a vacuum moldingprocess or can be thicker blocks of material with formed or machinedcavities. An array of LED packages 500 on a lead frame 510 is providedwith an LED die 520 and wire bonds 530 in the packages. The LED packagesare filled with an uncured encapsulant resin 540. The uncuredencapsulant resin is exposed to actinic radiation as described in U.S.Pat. No. 7,192,795 B2 (Boardman et al.), to at least partially cure theencapsulant resin to produce a partially cured encapsulant resin 550that has increased in viscosity significantly or has gelled, such thatthe resin does not flow out of the LED package when the packages on thelead frame are tilted or turned over. The surface of the partially curedencapsulant resin has at least some tackiness or is sticky. To a mold525 with cavities 535 designed to align with the packages on the leadframe is added uncured lens resin material 545. The array of packageswith partially cured encapsulant 550 is aligned with the mold 525, whichhas cavities filled with uncured lens resin material 545. The packagesare contacted to the mold. The assembled mold is again irradiated withactinic radiation through the mold material 525 to give partially curedlens resin 555. The assembly is then heated to finish curing theencapsulant and lens resins to give a single cured encapsulant lensmaterial 570. In general, the resins are considered bonded together inthe sense that they are not easily separated. The mold 525 canoptionally be removed to give an array of LED devices with lenses 580.As shown in FIG. 5 b, if partially cured resin 555 is cured to the pointof being tack free on it's surface, which is in contact with the mold525, the mold 525 can be removed prior to the heating step.

Another embodiment of the molding process is shown in FIG. 5 c in across sectional perspective and illustrates an alternative process flowfor the case where the mold material is transparent to the actinicradiation needed to cure the encapsulant and lens material. To a mold525 with cavities designed to align with the packages on a lead frame isadded uncured lens resin material 545. The uncured lens resin 545 in themold is exposed to actinic radiation to produce a partially cured lensresin 555 that has increased in viscosity significantly or has gelled,such that the resin does not flow out of the LED package when thepackages on the lead frame are tilted or turned over. To the LEDpackages 500 is added an uncured encapsulant resin 540. The mold withthe partially cured lens resin 555 is placed in contact with the LEDpackages containing uncured encapsulant resin 540. The assembly isirradiated from the mold side with a sufficient amount of actinicradiation to at least partially cure the uncured encapsulant materialsurrounding the die and wire bond in the LED package. The assembly isthen heated to finish curing the encapsulant and lens resins to give asingle cured encapsulant lens material 570. The mold 525 can optionallybe removed to give an array of LED devices with lenses 580.

FIG. 5 d illustrates an additional process flow diagram for the casewhere the mold material may or may not be transparent to the actinicradiation needed to cure the encapsulant and lens material.Non-transparent molds can be made from a wide variety of materials suchas metals, opaque ceramics and opaque plastics. To a mold 525 withcavities 535 designed to align with the packages on the lead frame isadded uncured lens resin material 545. The uncured lens resin 545 in themold is exposed to actinic radiation to produce a partially cured lensresin 555 that has increased in viscosity significantly or has gelled,such that the resin does not flow out of the LED package when thepackages on the lead frame are tilted or turned over. To the LEDpackages 500 is added an uncured encapsulant resin 540. The encapsulantis exposed to actinic radiation as described in U.S. Pat. No. 7,192,795B2 (Boardman et al.) to at least partially cure the encapsulant resin toproduce a partially cured resin 550 that has increased in viscositysignificantly or has gelled, such that the resin does not flow out ofthe LED package when the packages on the lead frame are tilted or turnedover. The mold with the partially cured lens resin 555 is placed incontact with the LED packages containing partially cured encapsulantresin 550. The assembly is then heated to finish curing the encapsulantand lens resins to give a single cured encapsulant lens material 570.The mold 525 can optionally be removed to give an array of LED deviceswith lenses 580.

Another embodiment of the molding process is shown in FIG. 5 e in across sectional perspective. An array of LED packages 500 on a leadframe 510 is provided with an LED die 520 and wire bonds 530 in thepackages. The LED packages are filled with an uncured encapsulant resin540. The uncured encapsulant resin is heated, to at least partially curethe encapsulant resin, producing a partially cured encapsulant resin 550that has increased in viscosity significantly or has gelled, such thatthe resin does not flow out of the LED package when the packages on thelead frame are tilted or turned over. The surface of the partially curedencapsulant resin has at least some tackiness or is sticky. To a mold525 with cavities 535 designed to align with the packages on the leadframe is added uncured lens resin material 545. The array of packageswith partially cured encapsulant 550 is aligned with the mold 525 filledwith uncured lens resin material 545. The packages are contacted to themold. The mold package assembly is then heated to finish curing theencapsulant and lens resins to give a single cured encapsulant lensmaterial 570. The mold 525 can optionally be removed to give an array ofLED devices with lenses 580.

As shown in FIG. 5 f, after contacting the LED packages with the mold,the uncured lens resin 545 can be partially cured either with actinicradiation or heat or both actinic radiation and heat, to producepartially cured lens resin 555 inside the mold. Note that if actinicradiation is to be used that the mold material must be transparent tothe actinic radiation. If the partially cured lens resin 555 is cured tothe point of being tack free on it's surface, the surface that is incontact with the mold 525, the mold 525 can be removed prior to thefinal heating step.

Another embodiment of the molding process is shown in FIG. 5 g in across sectional perspective and illustrates an alternative process flow.To a mold 525 with cavities 535 designed to align with the packages on alead frame is added uncured lens resin material 545. The uncured lensresin 545 in the mold can be exposed to either or both actinic radiationand/or heat to produce a partially cured lens resin 555 that hasincreased in viscosity significantly or has gelled, such that the resindoes not flow out of the LED package when the packages on the lead frameare tilted or turned over. The exposed surface of the partially curedlens resin, not in contact with the mold, has at least some tackiness oris sticky. To the LED packages 500 is added an uncured encapsulant resin540. The mold with the partially cured lens resin 555 is placed incontact with the LED packages containing uncured encapsulant resin 540.The assembly is then heated to finish curing the encapsulant and lensresins to give a single cured encapsulant lens material 570. The mold525 can optionally be removed to give an array of LED devices withlenses 580.

Another embodiment of the molding process is shown in FIG. 5 h in across sectional perspective. An array of LED packages 500 on a leadframe 510 is provided with an LED die 520 and wire bonds 530 in thepackages. The LED packages are filled with an uncured encapsulant resin540. The uncured encapsulant resin is exposed to heat or a combinationof heat and actinic radiation, to at least partially cure theencapsulant resin, producing a partially cured encapsulant resin 550that has increased in viscosity significantly or has gelled, such thatthe resin does not flow out of the LED package when the packages on thelead frame are tilted or turned over. The surface of the partially curedencapsulant resin has at least some tackiness or is sticky. To a mold525 with cavities designed to align with the packages on a lead frame isadded uncured lens resin material 545. The uncured lens resin 545 in themold can be exposed to either or both actinic radiation and/or heat toproduce a partially cured lens resin 555 that has increased in viscositysignificantly or has gelled, such that the resin does not flow out ofthe LED package when the packages on the lead frame are tilted or turnedover. The exposed surface of the partially cured lens resin, not incontact with the mold, has at least some tackiness or is sticky. Thepackages and the mold with partially cured encapsulant and lens resinsrespectively are contacted to one another. The mold package assembly isthen heated to finish curing the encapsulant and lens resins to give asingle cured encapsulant lens material 570. The mold 525 can optionallybe removed to give an array of LED devices with lenses 580.

Another embodiment of the molding process is shown in FIG. 5 i in across sectional perspective. An array of LED packages 500 on a leadframe 510 is provided with an LED die 520 and wire bonds 530 in thepackages. The LED packages are filled with an uncured encapsulant resin540 that is highly thixotropic or viscous such that the uncuredencapsulant resin does not flow out of the LED package when the packageson the lead frame are tilted or turned over. The surface of the uncuredencapsulant resin has at least some tackiness or is sticky. To a mold525 with cavities designed to align with the packages on a lead frame isadded uncured lens resin material 545, that is highly thixotropic orviscous such that the uncured lens resin 545 does not flow out of theLED package when the packages on the lead frame are tilted or turnedover. The exposed surface of the uncured lens resin, not contact themold, has at least some tackiness or is sticky. The packages and themold with uncured encapsulant and lens resins respectively are contactedto one another. The mold package assembly is then heated to finishcuring the encapsulant and lens resins to give a single curedencapsulant lens material 570. The mold 525 can optionally be removed togive an array of LED devices with lenses 580.

FIG. 6 is a schematic diagram of exemplary LED device 600 with one wirebond 630 bonded to LED die 610. The LED die is connected to electrodes620 a and 620 b, which are disposed on substrate 670. As shown in FIG.6, the process can be modified such that the LED packages may be filledwith multiple layers of encapsulant as has been previously described inU.S. Ser. No. 11/741,808 (Thompson et al.). The final LED device 600 canhave at least two different resins comprising the layers of theencapsulant lens material 570 from FIGS. 5 a-i. Examples of possiblecases are: 1. where the cured resin materials 650 and 660 are derivedfrom the same uncured resin material and the cured encapsulant resin 640is derived from a different uncured resin material. The refractiveindexes of all of the resin materials can be substantially the same orthe refractive index of the cured encapsulant resin material 640 ishigher than resins materials 650 and 660. Additionally, the curedencapsulant resin material 640 may be softer than cured resin materials650 and 660; 2. where the cured resin materials 640, 650, and 660 areall derived from different uncured resin materials. It may be desirablefor the refractive indexes of the three layers to decrease from curedencapsulant resin 640, to cured resin 650, to cured resin 660. It may bealso be desirable for cured encapsulant resin 640 to be soft with curedresin materials 650 and 660 being harder and more mechanically robust.It will be appreciated that the FIG. 6 is illustrative only and thatthere may be more than three layers in the final cured encapsulant lensmaterial.

It will be appreciated that the any of the layers of the resin materialdescribed in the preceding text may contain phosphor materials.

1. A method of making a light emitting device, the method comprising:(a) providing an LED package comprising an LED die disposed in areflecting cup, the reflecting cup filled with a firstphotopolymerizable composition such that the LED die is encapsulated,and partially polymerizing the first photopolymerizable composition toform a first partially photopolymerized composition, wherein partiallypolymerizing comprises applying actinic radiation having a wavelength of700 nm or less; (b) providing a mold having a cavity filled with asecond polymerizable composition; (c) contacting the first partiallyphotopolymerized composition and the second polymerizable composition;(d) polymerizing the first partially photopolymerized composition andthe second polymerizable composition to form first and secondpolymerized compositions, respectively, wherein the first and secondpolymerized compositions are bonded together; and (e) optionallyseparating the mold from the second polymerized composition.
 2. Themethod of claim 1, wherein contacting the first partiallyphotopolymerized composition and the second polymerizable compositioncomprises inverting the LED package.
 3. The method of claim 1, whereincontacting the first partially photopolymerized composition and thesecond polymerizable compositions comprises inverting the mold.
 4. Themethod of claim 1, wherein the second polymerizable compositioncomprises a second partially polymerized composition.
 5. The method ofclaim 1, wherein the first photopolymerizable composition and/or thesecond polymerizable compositions are thixotropic.
 6. The method ofclaim 1, wherein the first photopolymerizable composition comprises aresin selected from the group consisting of silicon-containing resinscomprising silicon-bonded hydrogen and aliphatic unsaturation, epoxysilicones, and (meth)acrylated silicones.
 7. The method of claim 1,wherein the second polymerizable composition comprises a resin selectedfrom the group consisting of silicon-containing resins comprisingsilicon-bonded hydrogen and aliphatic unsaturation, epoxy silicones, and(meth)acrylated silicones.
 8. The method of claim 1, wherein the secondpolymerizable composition comprises a multi-functional (meth)acrylate.9. The method of claim 1, wherein the first photopolymerizablecomposition and the second polymerizable compositions are the same. 10.The method of claim 1, wherein the second polymerized composition isharder than the first.
 11. The method of claim 1, wherein the firstpolymerized composition has a refractive index greater than that of thesecond.
 12. The method of claim 1, wherein the second polymerizedcomposition is harder than the first, and the first polymerizedcomposition has a refractive index greater than that of the second. 13.The method of claim 1, wherein the first photopolymerizable compositioncomprises two layers having the same or different composition.
 14. Themethod of claim 1, wherein the second polymerizable compositioncomprises two layers having the same or different composition.
 15. Themethod of claim 1, the mold comprising a mold material and being shapedto impart a positive or negative lens on a substantial portion of thesurface of the second polymerizable composition.
 16. The method of claim1, the mold comprising a mold material and being shaped to impartmacrostructures, each macrostructure having a dimension of from 10 um to1 mm.
 17. The method of claim 1, the mold comprising a mold material andbeing shaped to impart microstructures, each microstructure having adimension of from 100 nm to less than 10 um.
 18. The method of claim 1,wherein polymerizing the first partially photopolymerized compositionand the second polymerizable composition comprises applying actinicradiation having a wavelength of 700 nm or less.
 19. The method of claim1, wherein polymerizing the first partially photopolymerized compositionand the second polymerizable composition comprises simultaneouslyapplying actinic radiation having a wavelength of 700 nm or less andheating at less than 150° C.
 20. The method of claim 1, comprisingseparating the mold from the second polymerized composition to form amolded second polymerized composition, and the method further comprisingheating the molded second polymerized composition at less than 150° C.21. The method of claim 1, the LED die comprising a plurality of LEDdice.
 22. The method of claim 21, wherein each LED die of the LED diceemits light of substantially the same wavelength.
 23. The method ofclaim 21, wherein the LED dice emit light of different wavelengths. 24.The method of claim 1, wherein providing an LED package comprising anLED die disposed in a reflecting cup comprises providing a plurality ofLED packages disposed on a lead frame, each LED package comprising anLED die disposed in a reflecting cup.